Cerrejón Formation, Colombia: Earliest Record of Neotropical Forest

Late Paleocene fossils from the Cerrejón Formation, Colombia, are the earliest record of Neotropical rainforest



1. Scott L. Wing (a,1)
2. Fabiany Herrera (b,c)
3. Carlos A. Jaramillo (b)
4. Carolina Gómez-Navarro (b,d)
5. Peter Wilf (e)
6. Conrad C. Labandeira (a)



a. Department of Paleobiology, P.O. Box 37012, Smithsonian Institution, National Museum of Natural History, Washington, DC 20013;

b. Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Balboa, Ancon, Panamá, República de Panamá;

c. Florida Museum of Natural History and Department of Biology, University of Florida, P.O. Box 117800, Gainesville, FL 32611-7800;

d. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; and

e. Department of Geosciences, Pennsylvania State University, University Park, PA 16802

1. To whom correspondence should be addressed. E-mail: wings@si.edu

Abstract:

Neotropical rainforests have a very poor fossil record, making hypotheses concerning their origins difficult to evaluate. Nevertheless, some of their most important characteristics can be preserved in the fossil record: high plant diversity, dominance by a distinctive combination of angiosperm families, a preponderance of plant species with large, smooth-margined leaves, and evidence for a high diversity of herbivorous insects. Here, we report on an ≈58-my-old flora from the Cerrejón Formation of Colombia (paleolatitude ≈5 °N) that is the earliest megafossil record of Neotropical rainforest. The flora has abundant, diverse palms and legumes and similar family composition to extant Neotropical rainforest. Three-quarters of the leaf types are large and entire-margined, indicating rainfall >2,500 mm/year and mean annual temperature >25 °C. Despite modern family composition and tropical paleoclimate, the diversity of fossil pollen and leaf samples is 60–80% that of comparable samples from extant and Quaternary Neotropical rainforest from similar climates. Insect feeding damage on Cerrejón fossil leaves, representing primary consumers, is abundant, but also of low diversity, and overwhelmingly made by generalist feeders rather than specialized herbivores. Cerrejón megafossils provide strong evidence that the same Neotropical rainforest families have characterized the biome since the Paleocene, maintaining their importance through climatic phases warmer and cooler than present. The low diversity of both plants and herbivorous insects in this Paleocene Neotropical rainforest may reflect an early stage in the diversification of the lineages that inhabit this biome, and/or a long recovery period from the terminal Cretaceous extinction.

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